ICS843004I-01 Datasheet, PDF (8/14 Pages) Integrated Circuit Systems – FEMTOCLOCKS-TM CRYSTAL-TO- 3.3V, 2.5V LVPECL FREQUENCY SYNTHESIZER

Integrated
Circuit
Systems, Inc.
ICS843004I-01
FEMTOCLOCKS™ CRYSTAL-TO-
3.3V, 2.5V LVPECL FREQUENCY SYNTHESIZER
TERMINATION FOR 2.5V LVPECL OUTPUT
Figure 3A and Figure 3B show examples of termination for 2.5V
LVPECL driver. These terminations are equivalent to terminat-
ing 50Ω to V_CC - 2V. For V_CCO = 2.5V, the V_CCO - 2V is very close to
ground level. The R3 in Figure 3B can be eliminated and the
termination is shown in Figure 3C.
VC C O=2. 5V
Zo = 50 Ohm
Zo = 50 Ohm
2,5V LVPECL
Driv er
2.5V
R1
R3
250
250
2.5V
+
-
R2
62.5
R4
62.5
VCCO=2.5V
Zo = 50 Ohm
Zo = 50 Ohm
2,5V LVPECL
Driv er
2.5V
+
-
R1
R2
50
50
R3
18
FIGURE 3A. 2.5V LVPECL DRIVER TERMINATION EXAMPLE
FIGURE 3B. 2.5V LVPECL DRIVER TERMINATION EXAMPLE
VCCO=2.5V
Zo = 50 Ohm
Zo = 50 Ohm
2,5V LVPECL
Driv er
2.5V
+
-
R1
R2
50
50
FIGURE 3C. 2.5V LVPECL TERMINATION EXAMPLE
CRYSTAL INPUT INTERFACE
The ICS843004I-01 has been characterized with 18pF paral-
lel resonant crystals. The capacitor values shown in Figure 4
below were determined using a 25MHz 18pF parallel reso-
nant crystal and were chosen to minimize the ppm error.
843004AGI-01
X1
18pF Parallel Crystal
XTAL_OUT
C1
33p
XTAL_IN
C2
27p
ICS843004I-01
Figure 4. CRYSTAL INPUt INTERFACE
www.icst.com/products/hiperclocks.html
8
REV. A FEBRUARY 11, 2005